Messages in this thread Patch in this message |  | | Date | Sat, 23 Dec 2000 13:37:37 +0100 | From | Jens Axboe <> | Subject | Re: cdrom changes in test13-pre2 slow down cdrom access by 70% |
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On Fri, Dec 22 2000, David Mansfield wrote: > Jens, > > The cdrom changes that went into test13-pre2 really kill the performance > of my cdrom. I'm using cdparanoia to read audio data, and it normally > reads at 2-3x. Since test13-pre2 it's down to .6 - .7x. I've reverted > the following files to the ones from test13-pre1 and it's back to > normal:
Humm, interesting.
> This is a huge patch, is there some way I could break it apart to see > what the relevant changes are?
The change affecting you is most likely the CDROMREADAUDIO change, where we now just read a single cdda frame at the time. This gives us less data per interrupt, and apparently this is more than a theoretical slowdown for you. Please try with attached patch. If this solves it (as it should), then we should probably try and do persistent allocation of a bigger buffer for things like this. Grabbing > 1 frame was disabled because multi-page allocation is not reliable.
--- drivers/cdrom/cdrom.c~ Sat Dec 23 13:27:33 2000 +++ drivers/cdrom/cdrom.c Sat Dec 23 13:30:39 2000 @@ -1985,7 +1985,7 @@ } case CDROMREADAUDIO: { struct cdrom_read_audio ra; - int lba; + int lba, frames; IOCTL_IN(arg, struct cdrom_read_audio, ra); @@ -2002,7 +2002,9 @@ if (lba < 0 || ra.nframes <= 0) return -EINVAL; - if ((cgc.buffer = (char *) kmalloc(CD_FRAMESIZE_RAW, GFP_KERNEL)) == NULL) + frames = ra.nframes > 8 ? 8 : ra.nframes; + + if ((cgc.buffer = (char *) kmalloc(CD_FRAMESIZE_RAW * frames, GFP_KERNEL)) == NULL) return -ENOMEM; if (!access_ok(VERIFY_WRITE, ra.buf, ra.nframes*CD_FRAMESIZE_RAW)) { @@ -2011,12 +2013,14 @@ } cgc.data_direction = CGC_DATA_READ; while (ra.nframes > 0) { - ret = cdrom_read_block(cdi, &cgc, lba, 1, 1, CD_FRAMESIZE_RAW); - if (ret) break; - __copy_to_user(ra.buf, cgc.buffer, CD_FRAMESIZE_RAW); - ra.buf += CD_FRAMESIZE_RAW; - ra.nframes--; - lba++; + ret = cdrom_read_block(cdi, &cgc, lba, frames, 1, CD_FRAMESIZE_RAW); + if (ret) + break; + __copy_to_user(ra.buf, cgc.buffer, + CD_FRAMESIZE_RAW * frames); + ra.buf += (CD_FRAMESIZE_RAW * frames); + ra.nframes -= frames; + lba += frames; } kfree(cgc.buffer); return ret; -- * Jens Axboe <axboe@suse.de> * SuSE Labs - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org Please read the FAQ at http://www.tux.org/lkml/
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